The present invention relates to spin-valve magnetoresistive heads, and more particularly to a pin-valve magnetoresistive head having on terminal sides laminations for applying a bias magnetic field to a free magnetic layer and a composite-type head and a drive using the same.
At present, an AMR (Anisotropic Magnetoresistive) device is most frequently used in a magnetic head mounted in a magnetic recording medium recording/reproduction apparatus such as an HDD (Hard Disk Drive). However, as recording density increases, a full-scale movement toward practical use of a spin-valve magnetoresistive magnetic head (hereinafter, an SVMR head) using a more sensitive SVMR (Spin-valve Magnetoresistive) film has started, and the commercial production of the SVMR head has begun.
A common SVMR head includes a basic lamination as shown in FIG. 1. A device part is formed of an SVMR film formed by layering an antiferromagnetic layer 102, a pinned magnetic layer 103, a nonmagnetic layer 104, and a free magnetic layer in the order described on a substrate 101. A width C of the device part serves as a magnetic sensitive part S for detecting a signal magnetic field Hsig from a magnetic recording medium such as a hard disk. The SVMR head has terminal parts T1A and T1B on both ends of the device part in the direction of the width C. In the terminal parts T1A and T1B, conductive electrode terminals 106A and 106B are provided on hard ferromagnetic layers 107A and 107B, for instance. The hard ferromagnetic layers 107A and 107B are magnetizing bias means for magnetizing the free magnetic layer 105 in the direction of an arrow (the direction of an axis of easy magnetization) from the terminal parts T1A and T1B.
FIG. 2 shows an SVMR head 200 of another type. The SVMR head 200 is of a type called a terminal overlay. A basic structure is equal to that of the SVMR head 100 shown in FIG. 1. An SVMR device part is formed by layering an antiferromagnetic layer 202, a pinned magnetic layer 203, a nonmagnetic layer 204, and a free magnetic layer 205 in the order described on a substrate 201. Hard ferromagnetic layers 207A and 207B are provided on the terminal part T2A and T2B sides. However, electrode terminals 206A and 206B of terminal parts T2A and T2B are formed on both ends of the device part so as to cover parts thereof. The overlay-type SVMR head 200 has the magnetic sensitive part S narrower than the device width C by the width of an overlay by the terminal parts T2A and T2B. Thus, the overlay-type SVMR head 200 is devised so that reading and reproduction can be performed even if the track width of the magnetic recording medium is narrowed as the magnetic recording density increases.
FIG. 3 shows yet another overlay-type SVMR head 300. An SVMR film is formed by layering an antiferromagnetic layer 302, a pinned magnetic layer 303, a nonmagnetic layer 304, and a free magnetic layer 305 in the order described on a substrate 301. Terminal parts T3A and T3B are formed by ferromagnetic layers 307A and 307B and terminal electrodes 306A and 306B covering both ends of the SVMR film. As the ferromagnetic layers 307A and 307B, single-layer hard ferromagnetic layers or single-layer antiferromagnetic layers are employed. A bias magnetic field to set the magnetization orientation of the free magnetic layer in the direction of an arrow is applied by a static magnetic field if the ferromagnetic layers 307A and 307B are the single-layer hard ferromagnetic layers, and by an exchange coupling magnetic field if the ferromagnetic layers 307A and 307B are the single-layer antiferromagnetic layers.
Unlike the above-described SVMR heads 100 and 200 shown in FIGS. 1 and 2, in the SVMR head 300 shown in FIG. 3, the SVMR film formed of the antiferromagnetic layer 302, the pinned magnetic layer 303, the nonmagnetic layer 304, and the free magnetic layer 305 extends from the terminal part T3A side to the other terminal T3B side. However, a part reacting to an external magnetic field as the SVMR head 300 is a part between the terminal parts T3A and T3B. Therefore, in this specification, a part of an SVMR head which parts includes an SVMR film and magnetically senses the signal magnetic field Hsig is referred to as a device part. Further, parts on both sides of the device part which parts include conductive electrode terminals and, in some cases, lamination parts formed below the electrode terminals may be referred to as terminal parts.
The SVMR head 100 applies a bias magnetic field from the hard ferromagnetic layers 107A and 107B on the terminal part sides to the free magnetic layer 105. Therefore, such an uneven state is entered that the bias magnetic field from the hard ferromagnetic layers 107A and 107B is strong on both ends of the free magnetic layer 105 and weak in a center part thereof. Accordingly, it is difficult to make the free magnetic layer 105 to act as a single magnetic domain, thus, in some cases, preventing the signal magnetic field Hsig from the magnetic recording medium from being detected with sufficient sensitivity.
Further, leakage magnetic fields from the hard ferromagnetic layers 107A and 107B extend as far as the pinned magnetic layer 103. Therefore, there is a problem of an inclination of the magnetization direction of the pinned magnetic layer 103 that should be fixed parallel to the signal magnetic field Hsig.
Moreover, the SVMR head 100, in its production process, has the SVMR film formed by layering the antiferromagnetic layer 102, the pinned magnetic layer 103, the nonmagnetic layer 104, and the free magnetic layer 105 in the order described on the substrate 101, and, normally, is etched thereafter to have the device part of a given size. By this etching, nonmagnetic parts N, which have such disordered crystal states as to lose magnetism, are formed on both ends of the device part. The nonmagnetic parts N are also formed on both ends of the free magnetic layer 105 reacting to the signal magnetic layer Hsig. This causes a problem that the width of the device part for magnetic sensing becomes narrower than is designed and a problem that noises are generated.
The overlay-type SVMR head 200 shown in FIG. 2 has the device part formed by etching as the SVMR head 200 of FIG. 1. If the electrode terminals 206A and 206B are to be formed to exactly cover the above-described nonmagnetic parts N, the SVMR head 200 can be formed to maintain its sensitivity and have a narrower device width. However, it is very difficult to position the electrode terminals 206A and 206B exactly on the nonmagnetic parts N in the production process. Further, both ends of the free magnetic layer 205 which ends are overlaid with the electrode terminals 206A and 206B still functions as a free magnetic layer. Therefore, both ends of the free magnetic layer 205 react to the signal magnetic field Hsig, which may cause noise generation. Further, in the case of reading a hard disk having a narrow track width, these parts read adjacent tracks, thus causing so-called crosstalk to be generated.
Further, the overlay-type SVMR head 300 has the ferromagnetic layers 307A and 307B flatly contacting the free magnetic layers 305 to apply the strong bias magnetic field thereto from the terminal parts. However, if the ferromagnetic layers 307A and 307B are single-layer hard ferromagnetic layers, it is difficult to secure a sufficient thickness in the terminal parts. This prevents application of a bias magnetic field required for controlling the magnetization direction of the free magnetic layer 305, thus precluding the device part from being sensitive to the signal magnetic field Hsig.
On the other hand, if the ferromagnetic layers 307A and 307B are single-layer antiferromagnetic layers, the bias magnetic field is applied from the antiferromagnetic layers to the free magnetic layer 305 by the exchange coupling magnetic field. Normally, the bias magnetic field is in a range of approximately 100 to 400 Oe, and is caused by the signal magnetic field Hsig from the magnetic recording medium to rotate up to the free magnetic layer 305 existing in the terminal parts, thus causing noises to be generated.
A description will be given below in detail.
In this specification, a term xe2x80x9corientationxe2x80x9d is used to mean a given direction with an arrow or the like, and a term xe2x80x9cdirectionxe2x80x9d is used to mean the direction and a direction reverse thereto without considering the orientation.
Accordingly, an object of the present invention is to provide a spin-valve magnetoresistive head (an SVMR head) in which the above-described disadvantages are eliminated and a magnetic recording medium drive having such a head mounted therein.
The above object of the present invention is achieved by a spin-valve magnetoresistive head having a device part and terminal parts provided to both ends of the device part, the spin-valve magnetoresistive head including a first free magnetic layer formed from one to the other of the terminal parts and a lamination in the terminal parts on the first free magnetic layer, the lamination including an antiparallel coupling intermediate layer, a soft magnetic layer, and a first antiferromagnetic layer, the antiparallel coupling intermediate layer having a function of making front and rear magnetization orientation of a magnetic layer contacting the antiparallel coupling intermediate layer substantially antiparallel, the first antiferromagnetic layer applying to the soft magnetic layer a bias magnetic field substantially perpendicular to a direction of an external magnetic field to be detected.
In a preferred embodiment of the invention, the first antiferromagnetic layer applies the bias magnetic field to the soft magnetic layer in the terminal parts. A magnetization direction caused by the bias magnetic field is substantially perpendicular to a direction of a signal magnetic field Hsig from a magnetic recording medium. Here, being substantially perpendicular means being perpendicular or inclined within approximately xc2x110 degrees to the perpendicular state.
Further, the soft magnetic layer and the first free magnetic layer oppose each other with the antiparallel coupling intermediate layer being interposed therebetween in the terminal parts. The antiparallel coupling intermediate layer makes the magnetization orientations of the soft magnetic layer and the first free magnetic layer substantially antiparallel. Here, being substantially antiparallel means being parallel or inclined within xc2x110 degrees to the parallel state with a reverse magnetization orientation.
The soft magnetic layer and the first free magnetic layer are magnetically coupled to each other across the antiparallel coupling intermediate layer. That is, the magnetic fields of the soft magnetic layer and the first free magnetic layer come to draw one closed loop. On the other hand, the soft magnetic layer and the first free magnetic layer help each other against an external magnetic field to prevent their magnetization directions from being inclined.
In this SVMR head of the present invention, when the external magnetic field is zero, the magnetization direction of the first free magnetic layer is the same in the device part and in the terminal parts. On the other hand, when subjected to the signal magnetic field Hsig, the magnetization direction of the first free magnetic layer turns only in the device part. At this point, as previously described, the magnetization direction of the first free magnetic layer is insensitive in the terminal parts, being held by the soft magnetic layer and the antiparallel coupling intermediate layer. Accordingly, the magnetization of the first free magnetic layer is prevented from turning with respect to the signal magnetic field Hsig in the terminal parts.
A protection layer, an insulating layer, and/or a gap layer may be added to the above-described SVMR head as required.
Then, in the spin-valve magnetoresistive head, the antiparallel coupling intermediate layer may be preferably formed from the one to the other of the terminal parts through the device part, and a nonmagnetic layer, a pinned magnetic layer, and a second antiferromagnetic layer may be provided in an order described under the first free magnetic layer from a side thereof.
Further in the spin-valve magnetoresistive head, the antiparallel coupling intermediate layer and the soft magnetic layer may be preferably formed from the one to the other of the terminal parts through the device part, the soft magnetic layer may serve as a second free magnetic layer, and a nonmagnetic layer, a pinned magnetic layer, and a second antiferromagnetic layer may be provided in an order described under the first free magnetic layer from a side thereof.
Further in the spin-valve magnetoresistive head, the antiparallel coupling intermediate layer and the soft magnetic layer may be also preferably formed from the one to the other of the terminal parts, the soft magnetic layer may serve as a second free magnetic layer, and a nonmagnetic layer, a pinned magnetic layer, and a second antiferromagnetic layer maybe provided in an order described on the second free magnetic layer from a side thereof in the device part.
Further in the spin-valve magnetoresistive head, a nonmagnetic layer, a pinned magnetic layer, and a second antiferromagnetic layer may be preferably provided in an order described on the first free magnetic layer from a side thereof in the device part.
Further in the spin-valve magnetoresistive head, it is preferable that the first antiferromagnetic layer should have an exchange coupling magnetic field of 100 to 400 Oe with the soft magnetic layer or the second free magnetic layer. If the exchange coupling magnetic field falls within the range of 100 to 400 Oe, the first free magnetic layer can be magnetically fixed in a given direction through the antiparallel coupling intermediate layer in the terminal parts so as to be insensitive to the external magnetic field. On the other hand, the first free magnetic layer can be made to act as a single magnetic domain to be turned in the device part when the signal magnetic field Hsig is input.
Further in the spin-valve magnetoresistive head, it is preferable that the antiparallel coupling intermediate layer should include ruthenium.
Further, the present invention preferably includes a composite-type magnetic head having a magnetic head for reproduction and a magnetic head for recording, wherein the magnetic head for reproduction is a spin-valve magnetoresistive head including a device part, terminal parts provided to both ends of the device part, and a lamination including a first free magnetic layer formed from one to the other of the terminal parts, an antiparallel coupling intermediate layer in the terminal parts on the first free magnetic layer, a soft magnetic layer, and a first antiferromagnetic layer, the antiparallel coupling intermediate layer having a function of making front and rear magnetization orientation of a magnetic layer contacting the antiparallel coupling intermediate layer substantially parallel, the first antiferromagnetic layer applying to the soft magnetic layer a bias magnetic field substantially perpendicular to a direction of an external magnetic field to be detected.
Furthermore, the present invention preferably includes a magnetic recording medium drive including a magnetic recording medium and a composite-type magnetic head for recording and reproduction, the composite-type magnetic head opposing a surface of the magnetic recording medium, the magnetic recording medium drive including a spin-valve magnetoresistive head as a reproducing magnetic head part of the composite-type magnetic head, the spin-valve magnetoresistive head including a device part, terminal parts provided to both ends of the device part, and a lamination including a first free magnetic layer formed from one to the other of the terminal parts, an antiparallel coupling intermediate layer in the terminal parts on the first free magnetic layer, a soft magnetic layer, and a first antiferromagnetic layer, the antiparallel coupling intermediate layer having a function of making front and rear magnetization orientation of a magnetic layer contacting the antiparallel coupling intermediate layer substantially antiparallel, the first antiferromagnetic layer applying to the soft magnetic layer a bias magnetic field substantially perpendicular to a direction of an external magnetic field to be detected.